May 21, 2012 -- Two new studies show the early health risks the ever-enlarging number of obese U.S. teens face, from
diabetes to heart damage.

According to new research from the CDC, many overweight and obese teens who appear otherwise healthy already have heart disease risk factors such as high blood pressure. As many as 60% of obese teens are affected.

Many obese teens also have troubling physical changes in their heart, such as thicker heart muscle walls, according to another new study.

Even some teens who are normal weight have some heart disease risk factors, the CDC team found.

"Parents should be concerned and aware of these findings," says researcher Ashleigh L. May, PhD, an epidemiologist at the CDC.

"The main story here is that in addition to obesity, you need to be aware of these other potential risk factors for cardiovascular disease, that these risk factors are present relatively early," May tells WebMD.

The CDC study is published in Pediatrics, while the heart muscle findings are being presented today at the Heart Failure Congress 2012 in Belgrade, Serbia.

Teens and Heart Disease Risk: New Findings

The CDC researchers looked at nearly 3,400 teens and pre-teens, ages 12 to 19. They looked at 1999-2000 data and 2007-2008 data from a large national health study called NHANES (National Health and Nutrition Examination Survey).

As body mass index (BMI) rose, so did the risk factors, May tells WebMD.

"As weight increases, we observed an increase in the percentage of adolescents who had at least one cardiovascular risk factor," she says.

The researchers found at least one heart disease risk factor present in:

60% of obese teens

50% of overweight teens

37% of healthy-weight teens

May can't say why the healthy-weight teens had risk factors. "It could be poor diet, or lack of physical activity; we can't say for sure," she says.

The percent of teens who were found to have high blood pressure or be in danger of getting it didn't change between the two time periods.

Neither did the number who had high LDL or ''bad" cholesterol.

However, those who had diabetes or were in danger of getting it increased from 9% in 1999-2000 to 23% in the 2007-2008 survey.

However, May's team says this result "should be interpreted with caution," as they identified these youths by a one-time test for blood sugar levels. This single measure may not be totally dependable in children, May says.

Even so, the findings should be a call to action, the researchers say.

"Parents should be encouraging healthy lifestyles and should also be aware that these cardiovascular risk factors are present during adolescence," May says.

Teens and Heart Changes: New Findings

In a second study, European researchers measured heart size and tested heart function in 97 healthy teens, average age about 13.

The researchers found that the obese teens, even though they had no heart disease symptoms, had damaged hearts. They had thicker walls in the left ventricle, one of the heart's chambers.

As this wall thickens, heart problems are more likely later on in life.

Dejan Maras, MD, of Luton and Dunstable Hospital in London, is presenting the findings.

His team also found obese teens had a reduction in the speed of blood flow, both when the heart is pumping and when it is resting between beats.

Teens and Heart Disease Risk: Perspective

The message from the new research is pretty straightforward, says Reginald Washington, MD, chief medical officer of the Rocky Mountain Hospital for Children in Denver.

Washington, a member of the Obesity Task Force for the American Academy of Pediatrics, reviewed the findings for WebMD.

"The more you weigh, the harder your heart has to work to circulate blood through the body," he says. "That is a pretty simple concept for people to understand."

"If you add on top of that [excess weight], if you have high blood pressure, even mildly elevated, that also makes your heart work harder to circulate the blood."

The new European findings of a thicker heart wall in obese teens also make sense, he says. The heart muscle works harder in those who are obese, he says.

"Like any muscle, if you work it harder, it gets thicker," he says. Eventually, he tells WebMD, that thicker wall will put people at risk for heart problems.

"The more of these risk factors you have, the harder your heart has to work," he says.

Improved technology could be picking up more findings than before, Washington says. That could be a small piece of the new observations. But our ''obesogenic" society is likely playing a role, he says.

Teens and Heart Disease Risk: Parents' Plan

Washington finds many families are quick to blame genetics for their weight problems.

He tells them that genetics play a role but to consider another possibility: "Maybe your whole family is overweight because you all lead the same lifestyle," he says.

Parents can encourage their overweight or obese teens to make small changes, he says.

That tends to work better than declaring a major lifestyle overhaul.

Among his tips:

If your teen has three sodas a day, suggest he cut out one, to start.

Instead of two fast food cheeseburgers, order one.

Split an order of fries among the family.

Walk around the block after dinner, as a family.

Do what you can at home to promote a healthier lifestyle, and encourage your teen to follow it when she is away from home.

Some of these findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.